WORCESTER, Mass. -- City police are warning residents to be aware of their surroundings and to be cautious when walking alone or if approached by a stranger after three men were attacked at random as part of a possible knockout game.

In the past month, police have investigated attacks on the 700 block of Main Street, in the area of 87 Millbury St. and on Chatham near Main Street, all of which involved a male victim walking alone and being approached by another male whom the victims had never met, according to a police report.

Because the assaults are similar to others involving people participating in a violent activity called the "knockout game," police said that the suspects in the three Worcester attacks might be partaking in the game. The game's name refers to a "blitz style attack on a random unsuspecting stranger with the goal of knocking the person out with a single punch."

The knockout game was widely-reported in late 2013, as similar attacks occurred in cities throughout the country.

In Worcester, each attack involved male suspects punching the victims "in the face or head area with such force with the intent to inflict serious injury to the unsuspecting victim," according to a Monday-night police news release. The assailants were not provoked, police said.

Two of the three victims are 56-year-old males, while the third victim is a 23-year-old male. The two 56-year-old male victims were taken to local hospitals for treatment. The 23-year-old male was not seriously injured. It is unknown whether the assaults, though similar, were conducted by the same suspect or carried out by different individuals.

Investigators are working on these incidents and have limited suspect information at this time. If anyone has information about this incident, they can send an anonymous text TIPWPD + their message to 274637 or send an anonymous web-based message at worcesterma.gov/police. Calls can also be made to the Worcester Police Detective Bureau at (508) 799-8651.